/Engine/Plugins/Compositing/Composure/Source/Composure/Classes/ComposurePlayerCompositingTarget.h
If this component is set up to provide a preview window in editor (see GetEditorPreviewInfo), you can use this to customize the preview (to be something other than a world viewport). If this returns an empty pointer, then the preview will default to a viewport using theFMinimalViewInfodata fromGetEditorPreviewInfo().
virtual [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [SWidget](API\Runtime\SlateCore\Widgets\SWidget) > GetCustomEditorPreviewWidget()